Modular hot forming tool

ABSTRACT

A hot forming tool for the production of a press hardened sheet steel product includes an upper tool and a lower tool. At least one of the upper and lower tools has a base plate, a carrier tool mounted on the base plate, and a mold segment exchangeably received in the carrier tool and configured specific to the sheet steel product.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2014 107 210.3, filed May 22, 2014, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a hot forming tool for the production of a press hardened sheet steel product, to a hot forming line, and to a method for operating a hot forming line.

The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.

It is generally known in the art to shape metal products of hardenable steel alloys in their hot state and then to cool them down rapidly enough to effect quenching and ultimately hardening. Blanks are typically heated in a tempering station or furnace to a temperature above the austenitic temperature. The thus heated blanks are then transferred to a forming tool and shaped while being hot at least in part. In this way, the blanks are malleable to a greater extent compared to a cold state. The formed but still hot metal product is then rapidly cooled down to convert the austenitic regions into a martensitic and thus hard microstructure. This process is normally carried out in the forming tool, which is thus also referred to as a press hardening tool. The press hardening tool has cooling ducts to dissipate heat. As the press hardening tool is normally made of tool steel, the incorporation of cooling ducts in the press hardening tool becomes complex.

Hot forming and press hardening tools made of tool steel are constructed for the production of one particular sheet steel product. Sheet steel products involve structures for general machine construction, especially for motor vehicle construction, e.g. for the vehicle body and/or chassis. For example, motor vehicle pillars, door impact beams and such vehicle components like sills, roof pillars, etc. are produced using hot forming and press hardening technology.

It would therefore be desirable and advantageous to address prior art shortcomings and in particular to provide an improved hot forming tool which can easily be modified to allow a modular use thereof.

SUMMARY OF THE INVENTION

According to one aspect, of the present invention, a hot forming tool for the production of a press hardened sheet steel product includes an upper tool and a lower tool, at least one of the upper and lower tools having a base plate, a carrier tool mounted on the base plate, and a mold segment exchangeably received in the carrier tool and configured specific to the sheet steel product.

In accordance with the present invention, the provision of a basic tool is possible that has an upper tool and a lower tool which are movable towards one another, typically by lowering the upper tool toward the lower tool. The upper tool and/or lower tool, in turn, have a base plate upon which at least one carrier tool is mounted. The carrier tool may involve an attachment tool constructed to receive a mold segment or molding tool that is specific for a product to be produced. The carrier tool thus may have mounting points for the mold segment and in addition connections, such as cooling duct ports, via which the mold segment can be coupled to carry out the press hardening process. The carrier tool may be provided with tempering devices, e.g. in the form of an inductor, to maintain the mold segment at moderate temperature. As an alternative or in addition, the tempering device may itself be integrated into the exchangeable mold segment.

According to another advantageous feature of the present invention, the carrier tool may be exchangeably mounted to the base plate. This allows production of a motor vehicle structure, e.g. A pillar for the motor vehicle model Type 1. When the production line should now be converted to produce an analogous motor vehicle pillar of the motor vehicle Type 2, it is only required to exchange the product-specific mold segment because dimensions of the involved motor vehicle pillar are substantially the same. In the event, a transmission tunnel or roof pillar should be produced for example, however, the geometric dimensions are different. Thus, the type of motor vehicle structure to be produced changes so that a replacement of the carrier tool also becomes necessary. In other words, the carrier tool is also designed for exchange on the base plate.

According to another advantageous feature of the present invention, either one of the carrier tool and the mold segment can be configured for coupling with a quick-action clamping system and/or quick-action coupling system. In this way, retrofitting can be realized rapidly and effectively. For this purpose, actuators in particular are provided which can snap in and/or lock, for example electromechanically and/or pneumatically or by any other suitable manner. There is thus no need to secure the heavy, up to several hundreds kilogram, mold segments and/or carrier tools to a machine bed with a multiplicity of several hundred bolts. A mechanical locking can easily be released via the quick-action clamping system in order to allow exchange of the carrier tool and/or the mold segment and then to reattach them again by locking the quick-action clamping system. The quick-action clamping system or quick-action coupling system is hereby configured to allow attachment of possible through passages and/or connections, e.g. for passage of cooling liquid, in the absence of any particular retrofitting steps.

According to another advantageous feature of the present invention, the mold segment can be comprised of multiple parts in the form of mold sub-segments. The mold segment may hereby be subdivided transversely and/or longitudinally into single mold sub-segments. Advantageously, the mold sub-segments are insulated from one another in order to enable quenching and tempering of selected regions of the motor vehicle structure to be produced. Thus, the individual mold sub-segments can be maintained at different temperatures, especially cooled to different temperatures. This discriminative cooling may be implemented for example by the absence of a flow of cooling fluid or coolant to cooling duct ports of individual mold sub-segments. This, in turn, can be realized by using plugs, when placing the mold segment in the carrier tool. The presence of the plugs prohibits a flow of cooling fluid through the selected mold sub-segment. The use of respective valves, e.g. in the carrier tool, to prohibit or reduce a flow of coolant through the selected mold sub-segment, is, of course, also conceivable in order to decrease a cooling output in relation to the remaining mold sub-segments.

The mold segment represents the actual molding tool. Each of the upper tool and lower tool is configured to have a mold segment, with the mold segments of the upper and lower tools interlocking and bounding a mold cavity, when the hot forming tool is closed. A blank placed in the mold cavity is shaped into the sheet steel product. The sheet steel product contacts hereby the mold segments of the upper and lower tools and can be quench-hardened by cooling the mold segments.

According to another advantageous feature of the present invention, the carrier tool and/or the mold segment can be coolable. The mold segment may be cooled directly or the mold segment may be cooled indirectly. “Directly” coolable means that the mold segment itself is provided with cooling ducts and/or at least is in direct contact with a cooling fluid. This may be realized, for example, by providing a channel system on the backside of the mold segment and/or on the carrier tool so that cooling fluid conducted through the channel system comes into contact with the mold segment.

“Indirect” cooling means within the scope of the invention that the mold segment is devoid of any cooling duct but it is the carrier tool that is provided with a cooling duct system so that the mold segment is indirectly cooled, when the carrier tool cools down. Advantageously, the placement of a highly heat-conductive intermediary layer between carrier tool and mold segment is advantageous. Indirect cooling may supplement the direct cooling.

According to another advantageous feature of the present invention, the mold segment may be made of light metal, in particular from an aluminum alloy. Advantageously, a protective wear-resistant plate can be placed upon the mold segment. A highly heat-conductive intermediary layer may also be placed between the protective wear-resistant plate and the core segment. The protective wear-resistant plate may be exchangeably placed upon the core segment so that a wearing off of the protective wear-resistant plate can easily be addressed by simply replacing the worn-off plate with another protective wear-resistant plate. Thus, a hot forming tool according to the invention is easy to maintain and cost-effective. As an alternative, the mold segment may also be made of steel material, in particular tool steel.

When the hot forming tool according to the invention is intended for the production of a different sheet steel product, i.e. a product change is, for example, desired from the production of a B pillar to the production of an A pillar or roof pillar, the only requirement is a change of the mold segment. There is no need to produce a complete core with respective cooling duct system. This is beneficial because there is no need for expensive standby and storage costs for different complete tool assemblies or complete press facilities, and overall costs can be kept to a minimum as far as production of the actual molding tool is concerned because there is only need for replacing the mold segment. Also, product tolerances and/or modifications of the production process can be addressed in a rapid, simple and cost-effective manner by simple replacement or suitable modification of the mold segment. Handling of the mold segment, which is smaller in size than both the base plate and the carrier tool, is easy, and the mold segment can thus be produced cheaper and/or is easy to modify or store.

According to another advantageous feature of the present invention, the mold segment can be configured to include a cooling duct and/or a cooling duct system. Advantageously, the mold segment can have straight cooling ducts in the form of throughbores. These cooling ducts can easily be formed in the mold segment at little costs. To further enhance modularity of the hot forming tool, also the carrier tool can have cooling ducts and/or cooling duct ports for the mold segment, which may be standardized. This means within the scope of the invention that each replaceable mold segment has same connections for the cooling duct ports of the carrier tool so that a simple exchange of the mold segment enables a coolant introduced via the carrier tool to flow through the respective mold segment and to provide targeted heat dissipation to carry out quench-hardening. It may also be conceivable to use only some of the cooling duct ports of the carrier tool to cool only some regions in the mold segment.

According to another advantageous feature of the present invention, the carrier tool can have a receiving trough for receiving the mold segment at least in part. Currently preferred is a rectangular configuration of the receiving trough. The receiving trough has aligned openings between mold segment and carrier tool for conducting a cooling fluid. Suitably, a seal is provided in a transition zone of the openings. It is also conceivable to abut the mold segment and the carrier tool snugly against one another so as to attain a tightness sufficient to render any leakage of cooling fluid negligible.

According to another advantageous feature of the present invention, the cooling duct ports in the carrier tool can be formed in a bottom of the receiving trough or on opposite sidewalls of the receiving trough. In particular, when the cooling duct ports are formed on the sidewalls, coolant can be guided through the throughbores in the mold segment. When the cooling duct ports in the carrier tool are formed in the bottom of the receiving trough, coolant is introduced through the bottom into a cooling duct system of the mold segment.

It is also conceivable within the scope of the invention, in particular when the sheet steel product to be produced has overall small outer dimensions, to produce two or more sheet steel products at the same time. For this purpose, the base plate has mounted thereon two carrier tools in side-by-side disposition so that two mold segments are also arranged side-by-side. It is also possible to produce different steel sheet products in one forming process or during one press cycle. For example, pairs of vehicle pillars or roof pillars can be produced respectively. In other words, the left vehicle pillar and the right vehicle pillar of a motor vehicle type can be produced simultaneously in one press cycle by the hot forming tool.

According to another aspect of the present invention, a hot forming line for the production of a press hardened sheet steel product includes a heating unit, e.g. a furnace for heating a sheet steel blank, a hot forming tool receiving the sheet steel blank from the furnace for hot forming the sheet steel blank, the hot forming tool including an upper tool and a lower tool, at least one of the upper and lower tools having a base plate, a carrier tool mounted on the base plate, and a mold segment received in the carrier tool and configured specific to a sheet steel product being produced from the sheet steel blank, the mold segment being exchangeable with a different mold segment to enable production of different sheet steel products of same product type, and an optional cutting unit for trimming the hot formed sheet steel blank.

Transfer units, such as industrial robots, can be provided to transport the sheet steel product between the heating unit, forming tool and optional cutting unit or to transport away a produced sheet steel product.

A hot forming line according to the present invention can be retrofitted in a simple, efficient and cost-effective manner for the production of different products, without any need to replace or store an entire hot forming tool. When producing a motor vehicle pillar for small cars for example, and subsequently the hot forming line is desired for the production of a motor vehicle pillar of a midsize car, it is only required to exchange the mold segments. The furnace, e.g. a continuous furnace, is able to heat either one of the blanks, only the gripper device of the transfer units has to be reprogrammed or slightly modified. Thus, the hot forming and press hardening tool can be rapidly retrofitted through change of the mold segments. The hot forming line may also be converted in a similar rapid, efficient and cost-effective manner in the event of a change in the product type. For example, it is possible to first produce motor vehicle pillars and then produce structures that are significantly greater in dimensions, e.g. a transmission tunnel. The heating unit and the transfer unit can also be used in this case. Retrofitting by exchanging at least the mold segment and, optionally, also the carrier tool, renders the hot forming tool according to the present invention also useful for the production of a transmission tunnel. It thus becomes possible to store at a production site tools for the production of different motor vehicle structures in a cost-effective and space-saving manner and to implement the switch in the production through rapid tool change.

A hot forming tool according to the present invention can also find application in a situation in which it may be necessary for a change between two production batches of the same product, which are produced either directly in succession or interrupted as a result of a different product being produced in between, to exchange the mold segments because of wear and/or unacceptable product tolerances. In such a situation, it is especially easy to separate the hot forming tool according to the invention from a cooling circuit connection and to remove the mold segments from the carrier tools or to remove the carrier tools together with the mold segments from the hot forming tool and to replace them with new mold segments or new mold segments on the carrier tools. The previous carrier tools in particular may hereby be used again because it is the molding tool of the mold segment that is primarily responsible for the geometric precision and/or subject to wear. Thus, retrofitting times and times for maintaining a hot forming line, equipped with a hot forming tool according to the invention, is significantly reduced, thereby decreasing production costs.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 is a perspective view of a lower tool of a hot forming tool according to the present invention;

FIG. 2 is a plan view of the lower tool;

FIG. 3 is a sectional view of the lower tool, taken along the line III-III of FIG. 2; and

FIG. 4 is a sectional view of another embodiment of a hot forming tool according to the present invention.

FIG. 5 is a schematic representation of a hot forming line with a furnace, a hot forming tool according to the present invention and a cutting tool.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is shown a perspective view of a lower tool of a hot forming tool according to the present invention, generally designated by reference numeral 2. The hot forming tool 2 includes an upper tool, not shown here, and a lower tool 1. The lower tool 1 includes a base plate 3 which has mounted thereon two carrier tools 4 in side-by-side arrangement. Placed or at least received in part in the carrier tool 4 on the left-hand side of the drawing plane is a mold segment, generally designated by reference numeral 5. The carrier tool 4 on the right-hand side is shown without mold segment, and it is readily apparent that the carrier tool 4 has a receiving trough 6 of rectangular configuration. The mold segment 5, in turn, includes a bottom plate in the form of a mount 5 a and a molding tool 5 b which projects beyond the mount 5 a. Although not shown in FIG. 1, the upper tool has a molding tool that complements the molding tool 5 b and may also be part of an exchangeable mold segment. The receiving trough 6 has a bottom 7 which is formed with cooling duct ports 8 to conduct a coolant into the mold segment 5. Coolant is hereby introduced from the side via cooling duct ports 10 in a sidewall 9 of the receiving trough 6. The cooling duct ports 10 receive coolant from a not shown cooling facility, heat exchanger, or collector tank for guidance into the hot forming tool 2.

The mold segment 5 may be provided with not shown fasteners for detachable connection of the mold segment 5 to the carrier tool 4. Currently preferred is however a connection of the mold segment 5 to the carrier tool 4 by a not shown quick-action clamping system and/or quick-action coupling system.

FIG. 2 shows a plan view of the lower tool 1 of the hot forming tool 2. As is readily apparent, the mold segment 5 depicted on the left-hand of the drawing plane is used to produce a sheet steel product in the form of a B pillar. FIG. 2 is merely a simplified schematic illustration for ease of understanding of the invention. It is to be understood that in practice, both carrier tools 4 include a mold segment 5. The mold segment 5 is shown here, by way of example, as being subdivided into mold sub-segments 5.1, 5.2, 5.3, 5.4, 5.5 in a longitudinal direction indicated by arrow 18. As a result, the mold sub-segments 5.1, 5.2, 5.3, 5.4, 5.5 can be maintained at different temperatures. Optionally, an insulating layer may be arranged between two neighboring mold sub-segments 5.1, 5.2, 5.3, 5.4, 5.5.

FIG. 3 shows a sectional view of the lower tool 1, taken along the line of FIG. 2. As is readily apparent, the lateral cooling duct ports 10 of the carrier tool 4 feed into cooling ducts 11, respectively, which extend through the carrier tool 4 to the cooling duct ports 8 at the bottom 7 of the carrier tool 4. The cooling ducts 10 of the carrier tool 4 feed into cooling ducts or a cooling duct system 12 of the mold segment 5, in particular in the mount 5 a. The cooling ducts 11 are realized by straight bores and thus easy and cost-effectively to make. The cooling duct system 12 of the mold segment 5 may be sealed off by a plug, as shown for example in the right-hand region with respect to the drawing plane. As an alternative, it may be possible to provide solely in the mold segment throughbores which extend from left to right with respect to the drawing plane, with respective cooling ducts 11 extending in the mold segment 5 from one sidewall 9 to the opposite sidewall 9 in the receiving trough 6. Such an embodiment is shown by way of example in FIG. 4. Parts corresponding with those in FIGS. 1-3 are denoted by identical reference numerals and not explained again. In this embodiment, the mold segment 5 has a core segment 13 and a protective wear-resistant plate 14 which is placed upon the core segment 13. Throughbores 15 extend through the core segment 13 for direct cooling of the mold segment 5 and are fluidly connected with not shown cooling duct ports 10 of the carrier tool 4 that lead from one sidewall 9 to the opposite sidewall 9.

It is also conceivable within the scope of the present invention, to provide cooling duct ports 10 in the mold segment 5 only, while the carrier tool 4 is not configured for circulation of a coolant.

FIG. 4 further illustrates that both the upper tool 16 and the lower tool 1 have exchangeable mold segments 5 on the carrier tools 4. The carrier tools 4 may also be connected to the base plates 3 by quick-action clamping systems and/or quick-action coupling systems 19. The hot forming tool 2 is further provided with a downholder 17 which is movable in relation to the mold segments 5 and coupled with the lower mold segment 5. Although not shown in detail, it is also possible as an alternative to couple the downholder 17 directly with the carrier tool 4 and to exchange it separately from the mold segment 5. The downholder 17 extends hereby through the mold segment.

FIG. 5 shows a hot forming line including a furnace 20, the hot forming tool 2 according to the invention and a cutting tool 22, and transfer units 21 for transferring a steel sheet workpiece between the furnace 20 and the hot forming tool 2 and between the hot forming tool 2 and the cutting tool 22.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: 

What is claimed is:
 1. A hot forming tool for the production of a press hardened sheet steel product, comprising an upper tool and a lower tool, at least one of the upper and lower tools having a base plate, a carrier tool mounted on the base plate, and a mold segment exchangeably received in the carrier tool and configured specific to the sheet steel product.
 2. The hot forming tool of claim 1, wherein the carrier tool is exchangeably mounted to the base plate.
 3. The hot forming tool of claim 1, wherein at least one of the carrier tool and the mold segment is capable of being coupled with a quick-action clamping system and/or quick-action coupling system.
 4. The hot forming tool of claim 1, wherein the mold segment is comprised of multiple parts in the form of mold sub-segments, at least two of said mold sub-segments being coupled to one another via a thermal insulating layer placed there between.
 5. The hot forming tool of claim 1, wherein at least one of the carrier tool and the mold segment is coolable.
 6. The hot forming tool of claim 1, wherein the mold segment is made of light metal, in particular aluminum, or steel material, in particular tool steel.
 7. The hot forming tool of claim 1, further comprising a protective wear-resistant plate placed upon the mold segment.
 8. The hot forming tool of claim 1, wherein the mold segment is configured to include a cooling duct and/or a cooling duct system.
 9. The hot forming tool of claim 4, wherein the mold segment is configured for partial cooling, with the mold sub-segments in particular being coolable at temperatures that differ from one another.
 10. The hot forming tool of claim 1, wherein the carrier tool has cooling ducts and/or cooling duct ports for the mold segment.
 11. The hot forming tool of claim 10, wherein the cooling duct ports are capable of being coupled with the cooling ducts of the mold segment.
 12. The hot forming tool of claim 1, wherein the mold segment and the carrier tool have straight cooling ducts in the form of throughbores.
 13. The hot forming tool of claim 1, wherein the mold segment includes a mount and a molding tool sized to extend beyond the mount, with the mount and the molding tool being made in particular in one piece and of same material.
 14. The hot forming tool of claim 1, wherein the mold segment is cooled in at least one of two ways, a first way in which the mold segment is directly cooled, a second way in which the mold segment is cooled indirectly via the carrier tool.
 15. The hot forming tool of claim 1, wherein the carrier tool has a receiving trough for receiving the mold segment at least in part, in particular to receive a mount of the mold segment.
 16. The hot forming tool of claim 15, wherein the carrier tool has cooling duct ports for the mold segment, said cooling duct ports being arranged in a bottom of the receiving trough or in sidewalls of the receiving trough.
 17. A hot forming line for the production of a press hardened sheet steel product, comprising; a furnace for heating a sheet steel blank; a hot forming tool receiving the sheet steel blank from the furnace for hot forming the sheet steel blank, said hot forming tool comprising an upper tool and a lower tool, at least one of the upper and lower tools having a base plate, a carrier tool mounted on the base plate, and a mold segment received in the carrier tool and configured specific to a sheet steel product being produced from the sheet steel blank, said mold segment being exchangeable with a different mold segment to enable production of different sheet steel products of same product type; a cutting tool for cutting the steel sheet blank formed in the hot forming tool; and a transfer unit for transport of the sheet steel blank between the furnace and the hot forming tool and between the hot forming tool and the cutting tool.
 18. A hot forming line for the production of a press hardened sheet steel product, comprising; a furnace; a hot forming tool downstream of the furnace for hot forming a sheet steel blank, said hot forming tool comprising an upper tool and a lower tool, at least one of the upper and lower tools having a base plate, a carrier tool mounted on the base plate, and a mold segment received in the carrier tool and configured specific to a sheet steel product being produced from the sheet steel blank, said mold segment being exchangeable with a different mold segment, and said carrier tool being exchangeable with a different carrier tool to enable production of different sheet steel products of different product types; and a transfer unit for transport of the sheet steel blank between the furnace and the hot forming tool.
 19. A method for operating a hot forming line, comprising: separating a hot forming tool from an external cooling circuit port for initiating a product change between two different production batches; removing a mold segment or a combination of mold segment and carrier tool from a base plate of the hot forming tool; selecting another mold segment of a plurality of mold segments or another combination of mold segment and carrier tool of a plurality of mold segments and carrier tools; attaching the other mold segment or the other combination of mold segment and carrier tool onto the base plate of the hot forming tool; and reconnecting the hot forming tool to the external cooling circuit port. 